It was only by the time we arrived at Fuxingmen Bridge, the last bridge in the west before the city centre, and heard the steady crackle-crackle of small arms fire and the intermittent thud-thud of heavy machine guns that the enormity of what was happening dawned on us. It was 1am and in the warm June night air the usual crowd in vests and summer skirts were waiting on the flyover crossing the second ring road.

Before we took the scene in, a plump middle-aged woman was carried through the crowd. She was shaking with shock with a large gash across her forearm, and was bundled into a taxi. As the gunfire approached, the crowd behind became frantic and started ramming six articulated buses across the road into the hedgerows on either side.

Until then a tour of the suburbs had revealed the by now usual and farcical attempt by the army to enter. Out in the east towards the airport a few platoons of troops in battledress were shepherded by an excited crowd into barracks.

Swinging west along the third ring road, we found more convoys but now also signs of violence or force. The mood was sombre and edgier than it had been a fortnight ago when the soldiers had first come.

But even on Saturday afternoon there were ominous signs of the terror to come. Tiananmen Square was the usual spectacle of red flags blowing gaily, but behind the Great Hall of the People 1,000 troops were surrounded by a jeering crowd and the mood was ugly. Occasionally a student emerged holding aloft a captured helmet or showing off a bloody wound.

Littering the street towards Fuxingmen were half a dozen smashed-up army trucks or buses. Troops were trapped in one. Another was crammed full of gear and an AK-47 machine gun had been erected on top as an exhibition. The stream of cyclists drifting up and down were in high spirits, but there was an air of hysteria.

At around 2pm police loudspeakers had warned the crowd it was illegal to steal equipment from the People's Liberation Army, amid announcements that the troops would not use force but were there to protect the people.

Then 800 riot police stormed out of Zhongnanhai, the leadership's compound, firing tear gas and laying about them with clubs. The melÀe lasted half an hour and the police left.

Later, by the square, more troops were hemmed in by a crowd by the Revolutionary History museum. Students with "V" for victory T-shirts led the troops and onlookers in singing the Internationale.

Then at 7pm troops began pouring in. Forty trucks pulled into the eastern approach to the square just by the main diplomatic compounds and were stopped again. The soldiers clutched their guns and twisted nooses in their hands as they were loudly berated by angry grandmothers.

Leading them were trucks of toughs in plain clothes with yellow hardhats, wooden clubs and iron bars. They were surrounded by a crowd of 500 and several were almost beaten to death as they tried to escape. Unaware of this, diplomats brought their families out to watch the troops. All of this had failed to give us an intimation of what was in store. As the gunfire at Fuxingmen came closer, we began to run back in fear as the crowd began to set fire to the buses.

A tyre on our jeep had been slashed, but we rumbled down the street dodging in and out of the road barriers until we arrived at the Minzu Hotel, where an angry band of youths stormed our jeep, hurling stones and rocking us until we established our identity.

We dashed across to the hotel entrance, where a crowd was savagely beating a soldier. Another had found safety in the hotel and the crowd was trying to smash the doors. A police car was burning nearby.

The road was littered with broken glass and bricks. Just before, a detachment of riot police had been attacked, and the air was thick with tear gas and smoke.

The sound of gunfire and explosions grew closer and we tried to get into the hotel, finally finding a back entrance. First, a tank came past, then a dozen armoured personnel carriers, followed by hundreds of trucks from which troops fired constantly.

The crowd melted away but there were constant tracers and sparks as bullets ricocheted across the road. Some of the bullets were just "firecrackers", but others left holes in the lobby or dining hall windows. Lines of soldiers with clubs followed the trucks and buses.

On the truck stood a soldier cradling a machine gun. Some trucks were adorned with red banners saying, "the army loves the people".

From a window we could see shadowy figures flitting through the dark, hurling stones, and after an hour the last trucks moved down. One man siphoned off petrol from our jeep and hurled a Molotov cocktail, setting himself on fire.

Others smashed open the cars, including ours, trying to find transport to carry the wounded away. Later we found blood drying on the pavement, smeared across the car doors and drawn into circles under the hotel's revolving doors.

When the last truck had vanished towards the square, the crowd emerged clutching stones and sticks and moved off in pursuit.

Gradually the chants of "Tu Fei, Tu Fei" - the old nationalist cry of "Communist bandit" - grew louder and louder. Then they stopped and men in tears began singing the Internationale. People tore down the red pro-government banners draped down the sides of the hotel and burned them. More and more wounded were being taken to hospital nearby. We went to the small People's Hospital and it looked like an abbatoir. There were bodies on benches and beds or on blood-soaked mattresses on the floor. Many had gaping bullet wounds on the chest, legs, or head.

A doctor, voice hoarse with emotion, told us that 300 wounded had come in. "Most were so bad we sent them elsewhere. There were 35 seriously wounded and 70 others. Four have died, including a nine-year-old girl shot through the throat," he said. Students had rescued badly beaten soldiers and we saw one covered in blood who was clearly not going to live.

It was the same story at the nearby post office hospital. I began to feel sick. Another doctor said 12 people had died under his hands; out of 300 injured, 30 had died. There was not enough blood, and many bled to death as the exhausted staff could only operate three times in an hour. He thought 50 had died in every one of the 20 major hospitals in the capital.

The horror only worsened as we stood outside the hotel and people told us more and more stories. At the central post office, a journalist from the state news agency had been beaten to death, a family had died in their homes by stray gunfire, another man in his bathroom, a girl by a tear gas shell as she looked out of her window; four police had been dragged out of their car and beaten to death.

Students had been bayoneted to death, others had set fire to two armoured personnel carriers and trucks, tanks had crushed to death 11 students who had left the square and were lagging behind the others, more students had been crushed to death in their tents. "How could the Communist Party do this? How could they shoot children?" asked a worker in blue overalls. Others pleaded with us to tell the world what happened. The West must stop all investments, they said, and condemn their government. No one, not even the Japanese or the Kuomintang or the warlords, had ever done this, and this was their own government. But many were mute with horror. Nobody could find the words.

"All we wanted was some democracy," said a student who had been whipped across the face, his shoulders shaking with anger.